What does the pattern on the security door mean by an eye?

Don't let anyone outside see everything in the house. A cat's eye on the security door is both secure and discreet.

Concave lenses. The concave lens is a virtual image with upright and shrinking regardless of the distance. It is mounted on the outside of the door. >>>More

The patterns on the anti-theft door are pressed out of the mold, and the deep lattice is that the surface of the anti-theft door is very deep, which is the process that has come out in the past two years, and the price is a little more expensive than before. The main thing is that it looks good, and it has nothing to do with anything else. Hope you are satisfied.

The role of the anti-theft door chain.

The chain buckle is attached to the back of the door not far from the door, one end of the chain is fastened to the door frame, and the other end is movable and can be inserted into the chain latch on the back of the door to lock. When the anti-leeching chain is hung, the door can only be opened to about 5 8 cm at most, and people cannot pass through, and the hand cannot reach through the door to reach the chain buckle on the back of the door, which ensures that when the owner opens the door to confirm the identity of the visitor, he will not be suddenly attacked by the other party. Because the slide chain is easy to be forcibly cut by metal cutters and other tools, the anti-theft door chain is rarely used as a door lock alone, but only as an anti-theft auxiliary tool. >>>More

There are a total of 4 lenses in the cat's eye; 1 flat lens in the front and back, 2 concave and convex in the middle, facing each other in the front! As for the principle, I don't know much!